Effects of age, ambient temperature, and heat-stable Escherichia coli enterotoxin on intestinal transit in infant mice

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Abstract
Some interrelationships among age, ambient temperature, intestinal transit and enterotoxigenic E. coli infection were studied in an infant mouse model. The transit of dye in the small intestine was accelerated during the response to heat-stable E. coli enterotoxin. Transit in the small intestine of normal mice accelerated with increased age (from < 17 h-8 days old) and accelerated with increased ambient temperature (from 25-37.degree. C). Transit was more rapid in the jejunum than in the ileum throughout the range of experimental conditions studied. E. coli strains that do not produce any of the pili known to facilitate intestinal colonization were cleared from the small intestine more rapidly at 37.degree. C than at 25.degree. C. This clearance was possibly due to accelerated transit at the higher temperature. A strain of E. coli that produces K99 (pili that facilitate intestinal colonization in other species) was not cleared from the small intestine and colonized more intensively at 37.degree. C than at 25.degree. C. Intensified colonization by this strain was possibly due to increased production of K99 at the higher temperature. Sluggish intestinal transit may be characteristic of the neonates of other species and be 1 factor predisposing them to intestinal colonization by enteropathogens. This predisposition may be enhanced if the neonates are chilled. The effect of ambient temperature on intestinal transit in homeothermic neonates such as pigs, calves and humans may be different from that in mice because neonatal mice are poikilothermic.